In Flatpak releases before 1.18.1, a sandboxed application can replace the user‑specific ld.so file (~/.var/app/$appid/.ld.so) with a symbolic link. When Flatpak regenerates the LD cache, the symlink causes the process to write files under the user's home directory. The files created have predetermined names and contents, so the attacker cannot choose the file content or the exact target, but the write operation can overwrite or delete existing files, affecting user data.

The flaw affects all versions of Flatpak before 1.18.1. Default releases are 1.18.0 and earlier. Distributions that have not applied the upstream 1.18.1 update, including many Linux distributions still shipping older Flatpak versions, remain vulnerable. For long‑term support (LTS) releases, backported patches are available in the flatpak‑1.16.x branch, which also requires the cherry‑picked glnx changes glnx_chaseat_full and glnx_chase_and_mkdirat to fully harden the operation.

The CVSS score of 4 indicates a moderate severity level, and the vulnerability is not listed in the CISA KEV catalog. No EPSS score is currently available. The attack vector requires that an attacker already has the ability to run a malicious sandboxed application with the user’s privileges; this is therefore a local file write scenario. Because the attacker cannot control the file name or content, the complexity of exploitation is limited to creating the symlink and triggering cache regeneration, but the impact remains significant for the affected user environment. The likelihood of exploitation is uncertain without EPSS data, but the presence of the flaw could be discovered and exploited by a targeted adversary within the user’s local environment.